Since the Soviet Union put the first space station, Salyut 1, into operation 50 years ago, people have lived in orbit on a total of 11 such facilities. China will soon add another to this list. With the core module of the Chinese space station (CSS), which is scheduled to start at the end of April, the cumulation of a project that the country’s government originally planned for 1992 is finally entering the construction phase.
After the core module reaches space, China plans at least 10 more launches of other key modules, as well as missions with crew and cargo to complete the assembly of the station by the end of 2022. At that time, the CSS will join the International Space Station (ISS) as the only fully functional space station in orbit.
Put something together
The 100-ton T-shaped CSS will comprise three main modules: the 18-meter-long core module called Tianhe (“Harmony of the Heavens”) and two 14.4-meter-long experimental modules called Wentian (“Quest for the Heavens”) and Mengtian ( “Dreaming of the Heavens”) that are permanently attached to both sides of the core. As the station’s management and control center, Tianhe can accommodate three astronauts for stays of up to six months. When visiting astronauts and cargo ships, you will be connected to the core module from opposite ends. Both es and Wentian are equipped with robotic arms on the outside, and Mengtian has an airlock for maintenance and repair of experiments that are attached to the outside of the station. Tianhe has a total of five docking ports, so that an additional module can be added for future expansions. The station is designed for an operating time of more than 10 years.
The CSS has less than a quarter of the mass of the ISS – the largest and most expensive man-made structure in space, jointly built by 15 nations. “We had no plans to compete with the ISS in terms of size,” said Gu Yidong, chief scientist of the China Manned Space program. Instead, the three-module configuration is based on “China’s need for scientific experimentation” and “what we believe is a reasonable size for reasons of cost efficiency”.
To develop the CSS, China followed a three-stage strategy, first building manned spaceships (the Shenzhou missions), followed by mini-space stations (Tiangong-1 and 2) and the imminent launch of the multi-module station. The construction of the CSS was officially approved in 2010. Although China’s heavy-lift missile suffered a launch failure in 2017 that delayed Tianhe launch by more than a year, the country’s space leaders hope to stick to their goal of completing construction of the space station by 2022 through intensive launches over the next two years.
National and international experiments
The CSS will house 14 refrigerator-sized scientific experiment racks and some general-purpose racks that will provide power, data, cooling and other services for various research projects. There will also be more than 50 docking points for experiments that will be attached to the outside of the station to study how materials react to exposure in space. Science inside and out includes space physiology, life sciences, fluid dynamics, materials science, astronomy, and earth observation. So far, around 100 experiments have been selected from more than 800 domestic proposals, Gu says. Some of them could start collecting data as early as next year.
For example, the station will use the world’s most precise clocks and coldest atoms to aid basic research in general relativity and quantum physics. The clocks in the CSS are designed to have an incredibly low instability, with only one second of errors every three billion years. The experiment rack for ultracold atoms can cool atoms down to 10-10 Kelvin, the lowest temperature that can be achieved with current technologies. Some racks will be the first of their kind on a space station, including one dedicated to studying phase changes between the liquid and gas states of matter, as these processes become much more evident in weightlessness. For example, these studies could help develop smaller and more efficient cooling devices for spacecraft and even laptops.
The station will also reserve space and resources for a range of international experiments. Tricia Larose, a medical researcher at the University of Oslo, leads Tumors in Space, a 31-day experiment that will fly with the CSS and, among other things, test whether weightlessness can slow or stop the growth of cancer. As one of nine international projects selected by the China Manned Space Agency (CMSA) and the United Nations Office for Space Affairs (UNOOSA), the mission will use three-dimensional stem cell organoids, or “mini colon”, grown from cancer and are healthy Colon tissue from the same patient to study how DNA mutations are affected by weightlessness. “All previous cancer experiments in space have used two-dimensional cell lines,” says Larose. “In comparison, organoids mimic the structure and function of the organ and are the most physiologically relevant biosamples.”
Call for cooperation
CSS can count on a company a year or two after its completion: China is planning to launch a Hubble-sized telescope that will operate in the same orbit a few hundred kilometers away. As part of the CSS, the China Sky Survey Telescope (also called Xuntian) will have 300 times the Hubble field of view and cover a wide range of science in the near ultraviolet and optical wave ranges. The observatory will study cosmology, the large-scale structure of matter in the universe, galaxy and star research as well as dark matter and dark energy. It is designed to dock with the space station when necessary for servicing when necessary. It provides an easier, more economical, and “better way to hire astronauts to keep the telescope performing,” says Gu.
Xuntian has similar designs and goals to the European Space Agency’s Euclid Mission and NASA’s Nancy Grace Roman Space Telescope, both of which will launch in the coming years but will operate in complementary wavebands. Gu believes that the collaboration between the three telescopes and the exchange of observational data will lead to a deeper understanding of the universe and basic physics.
China welcomes the collaboration of scientists around the world at the CSS, stresses Gu. The collaboration between CMSA and UNOOSA will shortly publish a second call for international experiment proposals. Scientists can also apply for access to resources on the space station through institutional partnerships. However, it is not clear what level of international cooperation the CSS will receive due to geopolitical hurdles. US law severely prevents NASA scientists from working directly with China. In Europe, pressure from the agency is also making it difficult to get funding for projects that would affect the Chinese space program. Larose notes that she and her colleagues are “unexpectedly reluctant” to submit CSS-related grant applications. It’s frustrating, she says, because cancer knows no borders, and finding better cancer treatment benefits everyone in every country on earth. “When are we going to stop looking at our differences and focus on our similarities?” Asks Larose.